Written by:

Dr Diane Farrar

RM, BSc health science, BSc psychology, PhD reproductive endocrinology

Dr Diane Farrar is a practising midwife with over 25 years’ experience. She is a senior research fellow at the Bradford Institute for Health Research and visiting associate professor at the University of Leeds. Her research, which includes the areas of diabetes, high blood pressure, obesity and memory function, has been published in leading medical journals.

Pre-conception care for women who are overweight or obese

In this article:

  • How can a woman tell if she is overweight?
  • When in the month is the best time to try for a baby?
  • Can being overweight affect a woman’s fertility?
  • Losing weight in preparation for pregnancy
  • Are there any nutritional supplements recommended for obese women wishing to become pregnant?
  • Is weight loss surgery a suitable option?
  • Main points

Pre-conception care for women who are overweight or obese

Eating a well-balanced diet, exercising and maintaining a healthy weight throughout life gives the best chance of avoiding ill-health and many conditions including cancer, heart disease and diabetes. For women, being in the best possible health before pregnancy gives them the best chance of becoming pregnant, having a successful pregnancy and a healthy infant. As men supply half the genetic material needed for a baby it is important that fathers are in good condition (healthy weight, not smoking and limiting alcohol consumption) before conception too, though the influence of a woman’s health on her infant is greater, because of course it is the woman that carries her baby for nine months. There are many aspects to ‘being healthy’ such as eating well, being active and avoidance of hazardous substances such as tobacco and alcohol. It is important to know that compared to women who are a healthy weight, women who are overweight or obese have a greater chance of having a pregnancy complication. It is also important to remember though that the chance is small and most women that are overweight or obese will have no problems at all during pregnancy.

How can a woman tell if she is overweight?

Calculating body mass index is the most usual way of finding out whether a person is within the healthy weight range, underweight, or overweight. Body mass index (BMI) is a measure of weight and height, so there is a mathematical calculation: divide weight in kilograms (kg) by height in metres (m) and then divide the answer by height again to get BMI.

The World Health Organization has provided categories to describe different levels of weight for all people

BMI Classification
less than 18.5 Underweight
18.5 – 24.9 Normal weight
25 – 29.9 Overweight
30 – 34.9 Class I obese
35 – 39.9 Class II obese
40 upwards Class III obese

When in the month is the best time to try for a baby?

Becoming pregnant is most likely to happen if you have sex around 14 days after the first day of your last menstrual period, as this is when an egg is released, a process called ovulation. Eggs can only be fertilised for 12 to 24 hours following release so it is important to have sex during this time.

Can being overweight affect a woman’s fertility?

Yes, being overweight or obese can affect menstrual periods, and this may reduce a woman’s chance of becoming pregnant. Being overweight or obese can have a damaging effect on the regulation of the hormones needed to become pregnant to the extent that ovulation may be reduced or even stop. Being obese is linked to a condition called polycystic ovary syndrome (PCOS), women with PCOS can have hormonal imbalances which are linked to infertility.

The encouraging news is that weight loss, even modest weight loss (5% to 10% of total body weight), can lead to the normal hormone levels and a regular menstrual cycle and this can reverse infertility. So it is worth considering whether your menstrual cycle is regular (usually every 28 to 31 days) if you are having problems getting pregnant. If you are overweight then losing some or all of the excess weight may help regulate your menstrual cycle, making pregnancy more likely.

Losing weight in preparation for pregnancy

A healthy balanced diet is advisable whether you are maintaining or trying to lose weight.

So what does a healthy diet consist of and can this aid weight loss? A healthy diet is a balanced diet with limited processed foods. Processed foods are foods that are high in fat and sugar, such as fast foods (pizza/sausages) and pre-prepared convenience foods. Fruit and vegetables should make up a third of food eaten during each day; starchy foods such as bread and potatoes should make up another third; beans, pulses, fish and meat should make up around a sixth; and, lastly, oils, butter and treats such as biscuits and sweets should make up the remainder, (although this last group can be reduced, especially if weight loss is desired). It is also good to drink around two litres of water each day; this may help prevent overeating because thirst can be mistaken for hunger. Eating regular small meals may also help prevent overeating.

Weight loss programmes that include a support element are the most likely to be successful, so if you want to lose weight, joining a group programme or working to lose weight with a friend or group of friends should help you achieve your goal.

The calories you need to consume (or cut back on) each day to lose weight will depend on your weight and how much you would like to lose and over what time period, but it is important that weight loss is gradual (0.5 to 2lb per week) and that you receive all the nutrients you need each day. Your general practitioner or the leader of a weight loss programme will be able to advise you.

What is a moderate amount of physical activity? Many people are not as active as they should be, taking up a sport or hobby that includes exercise is great, but there are also simple changes to everyday life that will increase activity levels and fitness (and may help with weight loss). These changes include activities such as: walking to work or getting off the bus a couple of stops earlier than usual, parking further away from work and using the stairs rather than taking the lift. If you are unsure about what physical exercise you can do or you have a medical condition that may affect your ability to exercise or be active, seek the advice of your general practitioner before you begin.

Are there any nutritional supplements recommended for obese women wishing to become pregnant?

All women are advised to take folic acid at least one month before conception and during the first three months of pregnancy. Folic acid helps to reduce the risk of a baby being born with a neural tube defect, such as spina bifid. Because women who are overweight or obese (BMI of 30 or above) are at increased risk of their baby being born with a neural tube defect they are advised to take a dose of 5 milligrammes (mg) of folic acid. As well as being available as a supplement, folic acid is found in foods like leafy green vegetables, brown rice, granary bread, and breakfast cereals fortified with folic acid.

Vitamin D supplements are also recommended, not just for overweight or obese women but for all women. Iron supplements should only be taken by women who are anaemic (have low iron levels). Your midwife, GP or obstetrician will be able to advise you on taking supplements in pregnancy.

Is weight loss surgery a suitable option?

Increasing numbers of women are undergoing weight loss surgery; there are various types of surgery including gastric bypass, gastric banding and sleeve gastrectomy. It is important to know what type of surgery you have had, because food intake or food absorption may be affected differently and this may affect your growing baby.

Women who have had weight loss surgery do become pregnant, but they are advised to delay pregnancy for 12 to 24 months so that the time of very marked weight loss has passed. Women who have had weight loss surgery should see an obstetrician so that their pregnancy can be closely monitored as they may be at increased risk of having a small baby.

Main points

  • Being in the best possible health before pregnancy gives women the best chance of having a successful pregnancy and a healthy infant.
  • Women who are overweight or obese have a greater chance of having a pregnancy complication than women who are at a healthy weight.
  • Calculating body mass index is the most usual way of finding out whether a person is within the healthy weight range.
  • Being overweight or obese can affect menstrual periods and therefore reduce a woman’s chances of becoming pregnant. Obesity is also linked to polycystic ovary syndrome.
  • It’s advisable to adopt a healthy balanced diet if you are trying to lose or maintain weight.
  • Drinking around two litres of water each day may help prevent overeating because thirst can be mistaken for hunger.
  • If you would like to lose weight, joining a weight loss programme with a support element can help you achieve your goal and is the likeliest to be successful.
  • There are simple changes to everyday life, such as walking to work (if possible) and using stairs instead of lifts, that will increase activity levels and fitness and may help you lose weight.
  • Overweight women who are trying to get pregnant are advised to take a higher dose of folic acid (5mg).
  • If you’ve undergone weight loss surgery should wait for 12-24 months after their surgery before trying to conceive. Your pregnancy should also be monitored closely by an obstetrician.